There are a wide variety of metal covers that have been used in the construction industry to provide a building's outermost barrier to wind and water. They may be manufactured to resemble wood shake, slate, shingles, clay tiles or other non-metallic cover materials and may be installed on exterior walls or on roofs. More typically, however, metal roof covers utilize rather elongated metal panels installed along the slope of a roof.
Metal panel roofs utilize various flashings and other components where the fields of a roof terminate or intersect, such as the eaves, gables, valleys, ridges, and hips of a roof. Even in roofs having many different intersecting or overlapping fields, however, the basic construction of metal panel roofs across the expanse of a roof is fairly standard. Most commonly, an array of spaced, elongated support members or “purlins” is mounted across the structural rafters of a roof substructure. The purlins run horizontally across the rafters, i.e., across the slope of the roof. Layers of insulation and various barriers may be, and for climate controlled buildings usually are installed as well. Decking also may be provided for additional support. A cover is provided by a series of rather elongated, mostly flat, interconnected metal panels.
Each cover panel is typically about a foot to three feet in width. The lateral edges of the panels are bent in various configurations to form upwardly extending sides and a trough in the middle. The trough is where most of the water will be shed from the roof. Adjacent panels are joined along their upwardly extending sides to create relatively narrow seams which are elevated above the trough. The panels are laid out such that the seams run vertically, i.e., with the slope of the roof. The panels also may have one or more vertical ridges running through the trough, and it is those vertical seams and ridges that create the distinctive appearance that consumers associate with metal roofs. More importantly, however, since the seams between adjacent panels are formed a few inches above the troughs where most rain will be shed, metal panel roofs can be very resistant to leaking.
Skylights are widely installed to allow natural sunlight to enter a building through the roof. While problematic in roofs of all types, incorporating skylights in metal panel roofs present unique challenges. One approach has been to simply substitute a panel made from translucent fiberglass for a metal panel. That is, fiberglass panels are formed in more or less the same configuration, and installed vertically in more or less the same manner as the metal panels that are used in a roof. The fiberglass panel may occupy the entire run, or it may be truncated and extend through only a portion of the run. In the latter instance the truncated fiberglass panel is typically shingled into the run with truncated metal panels.
Such an approach has the advantage of simplicity, but fiberglass is more difficult to shape than metal panels with which it will be used. Substituting vertical fiberglass panels into an array of vertical metal panels, therefore, is practical only if the metal panels have a relatively simple shape. Corrugated panels may be used, as may be generally flat panels with simple raised geometry that allows the adjoining sides of the panels to overlap or nest. The sides of many metal panels, however, have relatively complex shapes and geometries which are intended to allow adjoining panels to be joined with a more leak resistant seam. It may be difficult or impossible to form fiberglass panels into a shape compatible with such panels.
Fiberglass panels also may not allow as much light to pass into a building as may be desired. Other materials, such as transparent or translucent plastics, allow more light to pass, but they have high coefficients of expansion. More significantly, their coefficient of expansion is much greater than metal panels with which they might be used. For example, an aluminum panel may expand and contract over a range of 2″ per 100 linear feet. A steel panel may expand and contract even less, perhaps over a range of 1″ per 100 linear feet. A similarly configured panel made from a plastic such as polycarbonate, however, may expand and contract over a range of 10″ per 100 linear feet. Thus, plastic panels have not been substituted into an array of metal panels, if at all, to any significant degree, and certainly not plastic panels of any substantial length. There would be quite a bit of shift between a plastic panel and the rest of a metal roof, and creating a seal around a plastic panel that will withstand years of cyclic expansion and contraction would be difficult or impossible.
Domed skylights also may be installed in standing seam metal roofs. They typically incorporate a flanged dome formed from transparent or translucent plastic and are commonly installed in the trough between the seams. Examples of such skylights are disclosed in U.S. Pat. No. 4,860,511 to K. Weisner et al. Conceptually, however, that approach, other than the provision of a molded dome, is not different that incorporating truncated plastic panels as discussed above. Thus, they suffer from the same difficulty in establishing a seal around the skylight.
Domed skylights, however, also create a restricted flow path for water being shed from the roof. Water can easily back up and reach the seams around a domed skylight. That is a greater concern in colder climates where ice dams can form around the skylight. Expanding the width of panels or reducing the width of a skylight is not a practical option for avoiding such restrictions. The width of panels is constrained by many other considerations, and narrow skylights are not always desired.
A domed skylight also may be mounted on top of a box-like structure or curb. Curbed skylights effectively raise the seam around the skylight to a level well above the trough where most run-off occurs. The curb itself, however, remains as an obstruction to water flow. A curb also effectively doubles the seams associated with a skylight, there now being seams between the skylight and curb and seams between the curb and the roof. Moreover, curbed skylights add significantly to the cost of the skylight itself and its installation, and mounting a curbed skylight to accommodate thermal expansion of a metal roof may be problematic.
Skylights also may have to support substantial weight even when they are not designed per se for that purpose and persons on the roof are advised to avoid stepping on the skylight. Fiberglass panels have relatively higher load capacities. The plastics from which translucent portions of domed skylights most commonly are fabricated, however, all other factors being equal, do not have the load bearing capacity of metal or fiberglass panels. Such considerations create design constraints and may require the installation of additional support components that make installation of skylights more difficult and costly.
Accordingly, there remains a need for new and improved systems, apparatus and methods for providing skylights in roof covers, especially standing seam metal roof covers. Such disadvantages and others inherent in the prior art are addressed by various aspects and embodiments of the subject invention.